During my Ph.D. work in electrical engineering, I used microfluidics, electromagnetics, and image analysis to build an automated system that captured and held a single yeast cell for study. This work was only superficially biology, though;the cell could have been a 5 urn bead. In my present postdoctoral position at Harvard University, I will complement my engineering skills in measurement and fabrication with the deeper understanding I need to design and conduct a biological experiment, my goal for the award is to learn cell biology, yeast genetics, classical genetic analysis, experimental evolution, and social evolution theory from my two mentors, Andrew Murray and Kevin Foster, to study one of the classical questions in evolutionary theory: How is cooperation among organisms and cells maintained under the threat of cheating? My experiments will study cellular cooperation and the maintenance of cooperation by examining how secreted enzymes (acid phosphatase and invertase) allow budding yeast, Saccharomyces cerevisiae, to harvest carbon and phosphorous from their environment. The project combines multiple complementary approaches, including molecular and cell biology, automated microscopy and image analysis, and computational models to interpret the experiments and produce testable predictions. My long-term goal is to direct an interdisciplinary lab at a research university studying microbial evolution. Disease cells such as cancer cells and pathogenic bacteria secrete enzymes that are central to their virulence, but sharing of secreted enzymes creates conditions that can favor "cheater" mutants that use the enzyme but do not make it. Understanding how such cheaters are discriminated against is fundamental to understanding the maintenance of cellular group behaviors and their associated pathologies. I will study enzyme secretion, cooperation, and cheating in budding yeast with the hope of applying insights from this work to medically important examples, particularly the release of secreted products by tumor cells.